give up, relinquish, step down, rid, leave, renounce, lay off, depart, foreswear, chuck up the sponge, more...

continue, persist, maintain, proceed, endure

cold turkey, gradual, patch, nicotine gum, nicotine patch, nicotine lozenge, nicotine inhaler, more...

select, click, few, heavenly, recent, mellow, post

leave or drop out,   pack it in,   refuse to continue,   resign one's job,   break the habit,   bow out, in a way,   drop out of school,   resigned, as a job,   give up informally,   called it quits